ar X iv : 0 70 8 . 34 96 v 3 [ he p -

A wealth of charmonium states have recently been reported in B meson decays. (For one review, see Ref. [1].) Until recently, all such states were neutral, implying the possibility of at least some fraction of cc̄ in their wave functions. Recently, however, the Belle Collaboration [2] has reported a state produced in B → Kπψ(2S) in which the πψ(2S) system displays a resonance-like structure with mass M = 4433 ± 4 ± 1 MeV and width Γ = 44 −13−11 MeV. This would be the first observation of a genuine tetraquark [3] charmonium configuration. The possibility of easily producing such configurations in B decays was noted, for example, in Ref. [4]. The purpose of this Brief Report is to suggest a mechanism for production of this state which relies upon the proximity of its mass to the D∗(2010)D1(2420) threshold. S-wave thresholds appear to be important in a wide variety of resonance-like behavior [5]. The X(3872) state produced (for example) in B → KX and decaying to ππJ/ψ lies 0.6 ± 0.6 MeV below DD ∗0 + c.c. threshold [6]. The Y (4260), seen in the radiative return reaction ee → γ + Y (4260) and in a direct ee scan, can be associated with the lowest threshold for which a cc̄ pair with J = 1 can materialize into a pair of mesons DD1(2420)− c.c. in a relative S-wave [5, 7]. The production mechanism we suggest for the πψ(2S) resonance-like state is based on the diagram of Fig. 1. The different charge states that can be involved in this process are summarized in Table I. The quarks q and q are independent. Isospin invariance implies B[B → Kπψ(2S)] = 2B[B → Kπψ(2S)] and B[B → Kπψ(2S)] = 2B[B → Kπψ(2S)]. The proposed mechanism operates by the production of an anti-charmed meson c̄q and a charmed meson cq̄ which then rescatter into cc̄ = ψ(2S) and qq̄ = π. A key feature of the data not answered by the present mechanism is why rescattering into J/ψπ is not observed. Perhaps the rescattering process is enhanced when the Q-values of the two sides are more nearly equal. The additional Q-value available in rescattering into states containing J/ψ may favor higher pion multiplicities, e.g., 3πJ/ψ or even 5πJ/ψ, over πJ/ψ [8]. [Here we have assumed a definite G-parity G(Z) = +.]